God Game
Well for instance I've seen some that use special rules for creating life(must fit xyz so that the definition of life is the same across all members), magic(must do xyz, again so that there aren't eleven different kinds of magic), and domains(one that used artifacts that could circumvent some rules, for those who chose acts within a particular domain).
Those make pretty interesting rules. I've run many god games, one even went eight aeons, so I get what you mean by guiding without making rules, GMs fiat is a good tool, but I've found that if you set expectations from the get-go for most obvious things, then you end up with players who like to play by those rules. Less problem children, so to speak.